35
Appendix B
due to a telephone ringing near the instrument, then only those seconds will contribute to the LAVG resulting in a level perhaps around 40 dB (notably lower than the actual levels in the environment).
Lavg = ER 
log2∫0RTIME 2LS ⁄ ER dt – log2 (RTIME)
dB
LEQ
The true equivalent sound level measured over the run time. The term LEQ is functionally the same as LAVG except that it is only used when the Exchange Rate is set to 3 dB and the threshold is set to none.
LE
The sound exposure level averages the sampled sound over a one second period. Assuming the sampled run time to be greater than one second, level exposure is the equivalent noise that would be equal in
energy to the noise that was sampled. SEL is typically measured using a 3dB exchange rate without a threshold. (LAE is not used by OSHA.)
LMn
Minimum SPL. Lowest SPL measured over a time interval.
LMx
Maximum SPL. Highest SPL measured over a time interval.
Logging
In sound studies, the saving of measurements at fixed intervals during a study, where each measurement is determined from data processed in the previous logging interval.
LPk
Peak SPL. This is the highest instantaneous value obtained during a study or a session. A peak SPL measurement is affected by the frequency response setting but not by the time response setting of the meter.
Noise
Unwanted sound.
Noise Floor
The signal magnitude at the bottom of the instrument’s linear range. Input signals below the noise floor cannot be differentiated from the internal noise of the instrument.
Sound Examiner
